In recent years, an inkjet recording method has been applied in various printing fields such as photography, various printing, special printing such as marking and production of color filters owing to its adaptability of image formation in a simple and low-cost manner.
An inkjet ink utilized in such an inkjet method includes a water-based ink comprised of water and a small amount of organic solvent, a non-water-based ink comprised of an organic solvent with almost no water, a hot-melt ink which is solid at room temperature and printed by being thermally melted, and an actinic ray curable ink which is cured by actinic rays such as light after printing. Any of these inks are selected based on specific requirement.
On the other hand, a sheet made of polyvinyl chloride as a water non-absorptive recording medium is utilized for a wide range of applications such as for outdoor signs which require long term weather resistance, and printing media which require adhesion to an object of curved surfaces. There are a plural number of methods to print on polyvinyl chloride; however, there is an inkjet recording method as a method which requires no plate making, a short preparation time, and is suitable for production in low members but for many types of products.
As an example of an inkjet ink capable of recording on the aforesaid polyvinyl chloride recording media, an inkjet ink containing cyclohexanone has been disclosed (please refer to Patent Document 1). Cyclohexanone exhibits a high solubility in polyvinyl chloride, and pigment in an inkjet ink dissolves into polyvinyl chloride, therefore excellent abrasion resistance can be obtained. Further, a non-water-based ink containing a solvent such as N-methylpyrrolidone is disclosed as a solvent exhibiting low odor, making it preferable with respect to a safer working environment compared to cyclohexanone (please refer to Patent Documents 2 and 3). Further, to improve a non-water-based ink incorporating a resin such as vinyl chloride-vinyl acetate copolymer and acryl has been disclosed (please refer to Patent Documents 4 and 5).
By use of these inkjet inks, an inkjet ink, which can considerably low odor and exhibits excellent abrasion resistance to polyvinyl chloride, can be prepared; however, there is a concern of environmental load due to the large amount of solvent vaporized during drying.
To counter this problem, disclosed has been vinyl film or a medium coated with vinyl to serve as a recording medium, on which a water-based pigment ink which is thermally fixed by use of a water-soluble resin (please refer to Patent Document 6). However, an ink containing resin represented by this document exhibits only short term storage stability. Further, a relatively good image can be prepared with a scanning type printer in which an image is formed by scanning an inkjet head several times, however, it exhibits only low image precision due to such as spottiness in a high speed system such as a 1-pass type printer in which an image is formed in one time scanning. Further, in the case of utilizing a water non-absorptive recording medium, compatibility of a higher print speed and image quality is difficult to achieve, which requires further improvement.                [Patent Document 1] Japanese Translation of PCT International Application Publication No. 2002-526631        [Patent Document 2] JP-A 2005-15672 (hereinafter, JP-A refers to Unexamined Japanese Patent Application Publication No.)        [Patent Document 3] JP-A 2005-60716        [Patent Document 4] JP-A 2005-36199        [Patent Document 5] International Patent Application Publication No. 04/007626 pamphlet        [Patent Document 6] JP-A 2005-113147        